<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script type="text/javascript" src="../assets/js/vue.js"></script>
    <title>methods Option</title>
</head>
<body>
<h1>methods Option</h1>
<hr>
<div id="app">
    {{ a }}
    <p><button @click="add(2)">add</button></p>
</div>

<script type="text/javascript">
    var app=new Vue({
        el:'#app',
        data:{
            a:1
        },
        methods:{
            add:function(num){
                if(num!=''){this.a+=num}
                else{this.a++}
            }
        }
    })
</script>
</body>
</html>